Diaphragm spring clutches are frequently used as starting clutches in connection with automatic transmissions in motor vehicles. A diaphragm spring frequently serves to deliver that contact pressure with which the clutch pressure plates and clutch disks, provided with a friction lining, are brought into frictional engagement with each other. In order to disengage the clutch, the pressure plate must be lifted off the allocated clutch disk, for which reason the diaphragm spring, which loads the pressure plate, must be moved against the pressure force applied thereby. In practice, the clutch release elements, moved by an actuator, engage with the diaphragm spring, via a suitable lever arm, so that the releasing force to be applied by the clutch release elements is, in any case, smaller than the pressure force to be applied by the diaphragm spring.
The actuator is controlled by a controller connected upstream thereof, which delivers the control variables for the actuator. The differences between single-disk, dry clutches and multi-disk, dry clutches, as well as drawn and pressed clutches, are not discussed in detail herein, since the functional principle is the same in all of these clutch types and the disadvantages, which will be described below, occur in equal measure. Basically pneumatic, hydraulic or electric actuators are taken into consideration as actuators, even though pneumatic or hydraulic actuators are predominantly used in automotive technology.
A basic disadvantage of the diaphragm springs in connection with vehicle clutches is their strongly non-linear releasing force characteristic, i.e., the curve of the releasing force over the releasing stroke. This releasing force characteristic is marked by very steep curves, with which the releasing force changes very strongly over a predetermined releasing stroke, alternating with very flat curves, with which essentially no force change occurs over a large releasing stroke.
The releasing force is non-linearly dependent on the releasing stroke according to this releasing force characteristic. This non-linear releasing force leads to a change of the travel amplification depending on the releasing stroke or the release position of the clutch release elements and the actuator. Herein the term “travel amplification” is understood as the reaction of the controlled system to a predetermined actuating variable of the actuator. The controlled system comprises for example a diaphragm spring, release bearing, release fork and actuator. This reaction of the controlled system to a predetermined adjustment variable can be accordingly changed depending on the position.
If this fact is not taken into consideration (for example, during the configuration of the controller), this leads to a very sluggish controller behavior (the times required to reach the desired position are very long) in areas with low travel amplification or the controller tends to vibrate in areas with a high travel amplification.
Against this background, the invention has the goal of creating a device for actuating a diaphragm spring clutch for vehicles in which the travel amplification is at least approximately identical over the entire releasing stroke and has a value at which the controller behavior is neither sluggish nor tends to vibrate.